The present invention relates to an audio signal processing technique.
Heretofore, there have been proposed techniques for imparting a vibrato component to an audio signal obtained by picking up a singing voice. For example, Japanese Patent Application Laid-open Publication No. HEI-7-325583 (corresponding to U.S. Pat. No. 5,536,902) (hereinafter referred to as “patent literature 1”) discloses a technique that imparts a desired audio signal with a sine wave adjusted in amplitude and cyclic period in accordance with a depth and velocity of a vibrato component extracted from an audio signal. Further, Japanese Patent Application Laid-open Publication No. 2002-73064 (hereinafter referred to as “patent literature 2”) discloses extracting a vibrato component from a singing voice and imparts a vibrato to an audio signal on the basis of the extracted vibrato component. Furthermore, “Vibrato Modeling For Synthesizing Vocal Voice Based On HMM”, by Yamada Tomohiko and four others, Study Report of Information Processing Society of Japan, May 21, 2009, Vol. 2009-MUS-80, No. 5 (hereinafter referred to as “nonparent literature 1”) discloses a technique for imparting a synthesized sound of a singing voice with a vibrato component approximated by a sine wave.
However, with the prior art techniques disclosed in patent literature 1 and non-patent literature 1, where a vibrato component is approximated by a simple sine wave, would present that problem that it is difficult to impart a natural vibrato component that is generally the same as that in an actual voice. The prior art techniques would also present a problem in imparting a variation component of other character elements than a pitch.